Techubox

IP Subnet & VLAN Planner

Subnet calculator plus a VLSM planner that carves CCTV, access control, BMS and other ELV VLANs from one block.

FreeNo sign-upRFC 950 / 1918 / 3021 / 4632CSV export

💾 Save stores the current inputs under this name in this browser (localStorage). Saved projects:

    IPv4 address

    Accepts 192.168.10.37/24, 192.168.10.37/255.255.255.0 or 192.168.10.37 255.255.255.0.

    Drag to try other subnet sizes for the same address.

    32-bit binary view

    Subnet details

    Inputs

    📘 Worked example
    🎓 How to use this tool
    1. Subnet calculator: type an address with its prefix, e.g. 192.168.10.37/24, or an address and a dotted mask. Results update as you type.
    2. Read the KPI tiles and the details table for the network, broadcast, first and last usable host, mask and wildcard. The binary strip shows which bits are network (blue) and which are host (green).
    3. Use the prefix slider to see how many hosts a /23, /25 or /27 gives for the same address.
    4. VLAN planner: enter the base block the client or IT team has given you, e.g. 10.20.0.0/22, and a growth allowance (30% is a sensible ELV default).
    5. Add one row per VLAN with its name, VLAN ID (1–4094) and the number of devices today, or tap a preset such as CCTV cameras or BMS and edit it.
    6. Check the verdict, the address-space map and the plan table. Red means a VLAN does not fit: enlarge the base block, reduce growth or split the system.
    7. Export the plan as CSV for the IP schedule or switch configuration, save the project in your browser, or print it to PDF for the submittal.

    Tips & common mistakes

    • Count every IP device, not just cameras: NVRs, encoders, PoE switches' management, door controllers, readers on IP, workstations and video wall controllers.
    • Gateways, HSRP/VRRP virtual IPs and DHCP servers use addresses too. Reserve them (tick “count the gateway”) and add extra hosts for a redundant pair.
    • Don't put ELV devices on VLAN 1 (the default VLAN). Keep management on its own VLAN and restrict it with ACLs.
    • Very large flat VLANs (more than about 500 hosts, typical) increase broadcast and multicast load; split big CCTV systems by building or floor.
    • /31 is only for point-to-point router links (RFC 3021) and /32 is a single host route; neither is a usable VLAN subnet.

    Standards & assumptions

    IPv4 subnetting per RFC 950 and CIDR per RFC 4632; private ranges per RFC 1918; shared address space RFC 6598; /31 point-to-point per RFC 3021; VLAN IDs per IEEE 802.1Q (1–4094). Preset host counts are typical starting values only. The result is for guidance and must be verified against the manufacturer's data, the client's IT addressing policy and local code.

    Techubox Engineering Tools · techubox.com/tools
    Scroll to Top